A continuous raster with a data depth of eight or less bits, and no colormap, will become a discrete raster of the same data depth with a colormap after being loaded into a geodatabase. This means the same file-based raster, which used the stretched renderer by default, will use the unique values renderer as the default after being loaded into a geodatabase.
In order to support a table for eight bit or lesser depth data in the geodatabase, a colormap table is created. Therefore, the data becomes discrete and color-indexed. By default it will be rendered with unique values, but will appear very similar as when it was a file-based raster layer.